Antipush stacker crane

ABSTRACT

The load carriage of a stacker crane is equipped with a vertical plate that is spring pressed to a position slightly in advance of the rearward vertical parts of load forks on the carriage, so as to engage the load first when the crane moves the forks horizontally toward a load engaging position. When depressed by contact with the load, the plate actuates a switch that stops the operation of the crane motor whereby to control stresses acting in the crane mast incidental to the movement of the forks against the load. In a further form, the forks are themselves mounted to yield so as to actuate the switch.

United States Patent Kang Suez Forrest City, Ark. [21 Appl. No. 769,093

[72] inventor [22] Filed Oct. 21,1968

[45] Patented Mar. 30, 1971 [73] Assignee Eaton Yale 8: Towne Inc.

Cleveland, Ohio [54] ANTIPUSH STACKER CRANE 3,034,674 5/1962 Quayle 3,268,097 8/1966 Armington Primary Examiner-Harvey C. Hornsby Att0rney-Teagno & Toddy ABSTRACT: The load carriage of a stacker crane is equipped with a vertical plate that is spring pressed to a position slightly in advance of the rearward vertical parts of load forks on the carriage, so as to engage the load first when the crane moves the forks horizontally toward a load engaging position, When depressed by contact with the load, the plate actuates a switch that stops the operation of the crane motor whereby to control stresses acting in the crane mast incidental to the movement of the forks against the load. In a further form, the forks are themselves mounted to yield so as to actuate the switch.

MOTOR I4 29 CONTROL CIRCUITS 30 3| MANUAL CONTROL Patented mh 30, 1971 3,572,516

2 Sheets-Sheet 1 v INVENTOR KANG SUEZ BYIQWQLZZV ATTORNEYS Patented -Marczl'n 30, 1971 7 3,572,516

2 Sheets-Sheet 2 F I MOTOR I4 CONTROL *6 25 CIRCUITS 3o 5 3! f 3 MANUAL 20 1 CONTROL 22 i:;:* z n9 INVENTOR J KANG SUEZ Byw wn ATTORNEY S ANTIPUSI'I STACKER CRANE This invention relates to stacker cranes, and more particularly to a stacker crane that will be less subject to stresses due to a misuse.

The cranes of the particular type are constructed with a mast that is supported at its upper end on a beam or track, and that is mounted for horizontal movement relatively to the beam or track. A load carriage is mounted for lifting movement on the mast, and there are power means that can be controlled by the operator of the crane so as to lift the carriage and to move the mast for handling a load.

Those skilled in the art appreciate that a stacker crane supports the load in position below the point at which the crane receives its support. Theoretically, the crane need accept no great amount of horizontal forces, and the crane may well be designed to accept the forces that are applied incidental to normal operation. However, a crane operator may try to use the crane in an improper manner, causing horizontal forces that are excessive. Thus, the operator sometimes will attempt to use the load carriage to push a load while the load is resting on a fixed surface. The load naturally resists pushing, and a movement of the crane then will apply very considerable forces horizontally, causing severe bendirg stresses in the mast and tending to tilt the entire crane on the beam. As will be appreciated, the stresses are most'severe when the load rests upon the floor, the load then acting at a point which is most distant from the point at which'the mast is mounted. Naturally, overstressing of the crane is hazardous and may cause considerable damage. The novel concept of my invention enables me to greatly reduce or even to eliminate this overstressing of a stacker crane.

In my invention, l equip the mast of a stacker crane with sensing means that will sense a relation between a load and the load carriage that moves vertically on the mast, the sensing means preferably being mounted on the load carriage. The load carriage is moved in a horizontal direction toward the load through operation of the usual power means that move the mast, and I arrange means through which the sensing means will act to control the stresses that must be accepted by the mast when the load carriage moves to position for engaging the load.

As a feature of my invention, I mount a yielding member in position to engage a load as the crane moves toward the load. Preferably, the yielding member is mounted to lie slightly in advance of a surface on the load carriage. The yielding member will yield with relative ease, causing but little stress on the mast while the load carriage moves toward the load. Together with the yielding member, I utilize switch means that will be effective for stopping the movement of the mast at about the same time or perhaps before the vertical surface of the carriage moves against the load.

In a form that I prefer, the yielding member is a vertical plate that is spring pressed to a position just forwardly of a vertical surface on the load carriage. That carriage surface may very well comprise rearward portions of a pair of load engaging forks, and I then mount the plate in position between those fork portions. Altemately, a load engaging member or fork may form the yielding member, in which case I support the member through a mounting that will yield while also constructed to accept the weight of the load. In any case, my invention enables me to construct a stacker crane that will not be overstressed incidental to a horizontal movement against a load. Then, as will be appreciated, the mast of the crane need not be overdesigned merely to accept forces that would be incidental to the pushing of a load, and I am able to solve a problem that has proven troublesome when building stacker cranes.

I have thus outlined rather broadly the more important features of my invention in order that the detailed description thereof that follows may be better understood, and in order that my contribution to the art may be better appreciated.

There are, of course, additional features of my invention that.

will be described hereinafter and which will form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception on which my disclosure is based may readily be utilized as a basis for the designing of other structures for carrying out the several purposes of my invention.

In the drawings:

FIG. I shows a side view of a stacker crane utilizing my invention.

FIG. 2 shows a front view of a portion of the crane, substantially on the line 2-2 of FIG. 1.

FIG. 3 is a sectional view showing certain control features, substantially on the line 3-3 of FIG. 2.

FIG. 4 is a sectional view showing a further construction that I may utilize in my invention.

Referring now more particularly to FIG. 1 of the drawings, I show a stacker crane having a mast 10 that is mounted on an overhead beam 11, an upper portion of mast 10 being equipped with mounting means l2 that support the mast in a vertical position below the beam. The mounting means 12 include trolley wheels 13 engaging the beam 11, and there is a drive motor 14 that will operate to move the mast It) on wheels 13 along the beam 11.

A load carriage I5 is mounted for lifting movement on the mast 10, as is usual in cranes 'of the particular type. In the construction that I h ve chosen to illustrate, load carriage I5 actually will move on a lower mast portion 16 that supports an operator's cab I7 and that may itself move vertically. I show a hydraulic lift ram I8 that may be utilized to effect the vertical movement. The load carriage is equipped with a pair of load forks I9, FIGS. 1 and 2, which are adapted to engage a load L that I have indicated by phantom lines in FIG. I. As will be appreciated, the forks I9 will be moved toward a load engaging position through operation of the drive motor 14 to move the mast l0 and its load carriage in a horizontal direction, after which the lift ram 13 may be actuated so as to lift the load L on forks 19.

In the concept of my present invention, I prefer to utilize a plate 20, FIGS. ll, 2 and 3, that I mount in a vertical position intermediate the rearward vertical portions of forks I9. As best shown in FIG. 3, a series of guide sleeves 2t are welded in rearwardly extending positions on the plate 20, and I assemble those sleeves in sliding relation on support shafts 22 that are welded to the load carriage IS. A coil spring 23 is arranged within each guide sleeve 21 and acts between the plate 20 and shaft 22 to press the plate in a forward direction. Further, I utilize bolts 24 that are inserted through openings in the plate 20 and that engage a threaded bore in each support shaft 22 so as to hold the plate 20 assembled to the load carriage I5. Bolts 24 are so adjusted that plate 20 normally will lie in a position projecting somewhat beyond the forward surfaces 25 on the vertical rearward parts of forks 19. It will thus be seen that plate 20 is mounted through a yielding means that support the plate while permitting it to move rather easily, and pressing the plate toward a predetermined position relatively to the forks.

Referring again to FIG. 3, I mount an electric switch 26 on the load carriage 15, as by a bracket 27. An operating member 28 on switch 26 is adapted to engage the plate 20, and is so positioned that a yielding movement of the plate will actuate the switch.

Conventional control circuits, indicated generally by the numeral 29 in FIG. It, may be utilized for the drive motor 14. As usual, there is a manual control 30 through which an operator in the cab 17 may actuate the control circuits 29 so as to control the operation of the motor I4. In my invention, I connect the switch 26 to the control circuits 29, as indicated diagrammatically by the line 31, so that actuation of switch 26 will be effective to stop the operation of drive motor I4.

To fully understand the operation of my invention, it will be best to consider FIG. I of the drawings. When the load L rests upon a fixed surface such as the ground, the drive motor M may be operated so as to move the load carriage 15 in a horizontal direction toward load engaging position, as I mentioned earlier. Where the load engaging members are forks, they will move substantially to the lifting position indicated in F 16. 1, with parts of the forks 19 under the load L and the vertical fork surfaces 25 juxtaposed or perhaps in contact with the rear surface of the load. Before the fork surfaces 25 engage the load, the plate 20 will yield so that drive motor 14 no longer will operate. The mast and load carriage perhaps will continue to move slightly farther, but the fork surfaces need accept no pressures as might be due to continued operation of the motor 14.

My stacker crane, including its mast 10, naturally is designed to withstand the stresses that are incidental to the lifting and handling of a load. Of course, some of those stresses will be due to forces acting in a horizontal direction. However, my invention enables me to eliminate those relatively tremendous stresses that horizontal forces would generate in the stacker crane should the crane be utilized to push a load along the floor. 1 thereby solve a considerable problem in the design of the mast, and there is less need to utilize a construction that is costly or that may be impractical due to the requirements of stacker crane design.

While I prefer to utilize the yielding plate 20, as l have described, l do not wish to limit my invention by the yielding plate and 1 may utilize a load engaging member 119 that will itself yield, and that is shown in FIG. 4. Thus, the load engaging member 119 may comprise a fork having a rather conventional shape, with a vertical surface 125 that is adapted to engage the rear surface of load L as the crane moves the fork to load engaging position. Secured to the rear surface of the fork 119 are guide sleeves 121 that engage support shafts 122 on the load carriage 15, much as l have described in connection with FIGS. 1 to 3. The sleeves 121 and shafts 122 in this form of my invention are designed to support the fork 119 together with its load, but sleeves 121 nevertheless will slide on the shafts 122 so as to yield rather easily when the crane moves the vertical fork surface 125 against the load L. l utilize a coil spring 123 acting between each shaft 122 and the fork 119, and a bolt 124 that will hold fork 119 in assembled position. P10. 4 also shows switch 26 mounted directly on the load carriage 15, with a bracket 127 mounted on one of the guide sleeves 121 for coacting with the switch operating member 28.

I believe that it will be unnecessary to describe in detail the operation of the construction that I show in F 10. 4, because it will act in much the same manner that I already have described in connection with the first form of my invention. In P16. 4, however, it will be understood that the actuation of switch 26 will be effected through yielding of the same member or fork 119 that lifts the load.

Having described the construction and operation of my invention, l believe that its very considerable value will be understood, and that its merits will be fully appreciated by those skilled in the art,

lclaim:

1. For a combination of the class described, a mast, a load carriage mounted for vertical movement along said mast for lifting a load, means mounting said load carriage for movement in a horizontal direction, a motor operable to move the load carriage horizontally on said mounting means and effective to place said carriage in position for lifting a load that rests on a fixed support, control means for controlling the operation of said motor, sensing means for sensing attempts to horizontally move a load against a predetermined resistance to horizontal motion, said sensing means comprising means capable of exerting a biasing force equal to said predetermined resistance for maintaining said carriage a predetermined minimum distance away from said mast and a switch means for sensing when said biasing force has been overcome horizontal motion.

2. In a combination of the class described, a mast, a load carriage mounted for movement along said mast for lifting a load, means mounting said load carriage for movement in a horizontal direction, a motor operating to move the load carriage on said mounting means and effective to place said carriage in position for lifting a load that rests on a fixed support surface, control means for controlling the operation of said motor, sensing means for sensing a relation between the load carriage and the load, said sensing means comprising a member for engaging the rearward surface of the load, a series of guide sleeves and a series of support shafts slidable in said sleeves and secured between said member and said load carriage to mount said member for movement in a fore and aft direction on said carriage, surfaces on said shafts and sleeves coacting effectively to support said member while holding said member in predetermined aligned relation to said carriage, a coil spring acting between each sleeve and its shaft to press said member in a forward direction on its mounting, a bolt assembled between each shaft and its guide sleeve and limiting a spring pressed movement of said member for holding said member in position to engage the rearward load surface when the motor moves the load carriage into a predetermined relation to the load, and a switch operated by said member when said member is depressed against its spring pressure by engagement with the load, and means through which said sensing means actuate said control means so as to control a movement of the load carriage relatively to the load.

3. The stacker crane of claim 2 wherein said sensing means also senses attempts to horizontally move a load against an abutting object.

4. In a stacker crane having a vertical mast mounted at its upper end portion for movements in a horizontal direction, a load carriage mounted for lifting movement on a lower portion of said mast, a motor operating to move said mast on its mounting and effectivefor moving the load carriage toward a load that rests on a fixed supporting surface, control means for controlling the operation of said motor, sensing means associated with said mast for sensing a movement of the load carriage to a position for lifting the load, said sensing means comprising a yielding member mounted in position on said load carriage to yield by contact with the load, and a switch connected to the motor control means and actuated by said yielding member, and means through which said sensing means actuate said control means so as to control bending stresses that may act in the mast incidental to said movement of the load carriage to load lifting position.

5. The combination set forth in claim 4 in which said sensing means comprise a member having a forward surface for engaging the rearward surface of the load, means mounting said member for movement in a fore and aft direction on said load carriage and including portions coacting to support said member in a predetermined aligned relation to said carriage, and spring means pressing said member toward a normal forward position on its mounting relatively to said carriage.

6. The combination set forth in claim 5, in which the means that mount said member comprise a series of guide sleeves in sliding relation to a series of support shafts, said spring means including a coil spring acting between each sleeve and its shaft, and a bolt assembled to each shaft and limiting a springpressed movement of said member on its mounting for holding said member in its normal position. 

1. For a combination of the class described, a mast, a load carriage mounted for vertical movement along said mast for lifting a load, means mounting said load carriage for movement in a horizontal direction, a motor operable to move the load carriage horizontally on said mounting means and effective to place said carriage in position for lifting a load that rests on a fixed support, control means for controlling the operation of said motor, sensing means for sensing attempts to horizontally move a load against a predetermined resistance to horizontal motion, said sensing means comprising means capable of exerting a biasing force equal to said predetermined resistance for maintaining said carriage a predetermined minimum distance away from said mast and a switch means for sensing when said biasing force has been overcome by resistance to horizontal movement and has caused said carriage to move closer to said mast than said predetermined minimum distance, and means through which said sensing means actuates said control means so as to control movement of the load carriage horizontally relative to a resistance to horizontal motion.
 2. In a combination of the class described, a mast, a load carriage mounted for movement along said mast for lifting a load, means mounting said load carriage for movement in a horizontal direction, a motor operating to move the load carriage on said mounting means and effective to place said carriage in position for lifting a load that rests on a fixed support surface, control means for controlling the operation of said motor, sensing means for sensing a relation between the load carriage and the load, said sensing means comprising a member for engaging the rearward surface of the load, a series of guide sleeves and a series of support shafts slidable in said sleeves and secured between said member and said load carriage to mount said member for movement in a fore and aft direction on said carriage, surfaces on said shafts and sleeves coacting effectively to support said member while holding said member in predetermined aligned relation to said carriage, a coil spring acting between each sleeve and its shaft to press said member in a forward direction on its mounting, a bolt assembled between each shaft and its guide sleeve and limiting a spring pressed movement of said member for holding said member in position to engage the rearward load surface when the motor moves the load carriage into a predetermined relation to the load, and a switch operated by said member when said member is depressed against its spring pressure by engagement with the load, and means through which said sensing means actuate said control means so as to control a movement of the load carriage relatively to the load.
 3. The stacker crane of claim 2 wherein said sensing means also senses attempts to horizontally move a load against an abutting object.
 4. In a stacker crane having a vertical mast mounted at its upper end portion for movements in a horizontal direction, a load carriage mounted for lifting movement on a lower portion of said mast, a motor operating to move said mast on its mounting and effective for moving the load carriage toward a load that rests on a fixed supporting surface, control means for controlling the operation of said motor, sensing means associated with said mast for sensing a movement of the load carriage to a position for lifting the load, said sensing means comprising a yielding member mounted in position oN said load carriage to yield by contact with the load, and a switch connected to the motor control means and actuated by said yielding member, and means through which said sensing means actuate said control means so as to control bending stresses that may act in the mast incidental to said movement of the load carriage to load lifting position.
 5. The combination set forth in claim 4 in which said sensing means comprise a member having a forward surface for engaging the rearward surface of the load, means mounting said member for movement in a fore and aft direction on said load carriage and including portions coacting to support said member in a predetermined aligned relation to said carriage, and spring means pressing said member toward a normal forward position on its mounting relatively to said carriage.
 6. The combination set forth in claim 5, in which the means that mount said member comprise a series of guide sleeves in sliding relation to a series of support shafts, said spring means including a coil spring acting between each sleeve and its shaft, and a bolt assembled to each shaft and limiting a spring-pressed movement of said member on its mounting for holding said member in its normal position. 